Td8g Dresser

My td8g has 2 year old with about 25 hours on it remand cummins 4bt engine in it. I’ve came to the conclusion that either the cam gear has came loose or the cam shaft is broken. What exactly holds the cam gear on, is it possible that it’s just loose on the cam end or do you think the shaft is broke. If it’s just the gear loose how would I go about putting everything back in time?

Td8g Dresser